Method for pickling coils

ABSTRACT

A METHOD FOR PICKLING COILS OF METAL STRIP OR WIRE WHEREIN THE COILS ARE CENTRALLY SUPPORTED, TO SUBMERGE INTO THE PICKLE, AND VIBRATION IS EMPLOYED TO PERIODICALLY SEPARATE THE COIL WINGINGS SO AS TO ENABLE ACCESS OF THE PICKLE THROUGHOUT THE WINDINGS. THE INVENTION TEACHES TO USE A VIBRATION FREQUENCY WHICH IS OUTSIDE THE SPECTRUM   OF NATURAL FREQUENCIES OF THE COIL WINDINGS, AND A MATCHED VIBRATION AMPLITUDE OF SUCH EXTENT THAT THE ACCELERATION OF FALL OF THE STOCK TO BE PICKLED IS EXCEEDED WHEREBY THE STOCK IS MOMENTARILY TAKEN OFF ITS SUPPORT.

y 7 R. SCHOFFMANN METHOD FOR PICKLING COILS Filed Dec. 30, 1968 INVENTOR.

RUOOL 54 Ho FFMA NN w M w United States Patent @fice 3,592,690 METHOD FOR PICKLING COILS Rudolf Schoffmann, Linz, Austria, assignor to Vereinigte Osterreichische Eisenund Stahlwerke Akfiengesellshaft, Linz, Austria Filed Dec. 30, 1968, Ser. No. 787,852 Claims priority, application Austria, Jan. 11, 1968, A 279/68 Int. Cl. B08b 3/00, 7/00 US. Cl. 134-1 2 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a method for pickling coils, which are suspended on a supporting device, immersed into a pickling bath and subjected to vibration by vibrators acting on said supporting device.

The pickling periods required for pickling tight coils of strip or wire are relatively long, as the individual windings of the coils are in close proximity in respect of one another. It is, therefore, not possible to safeguard free access of acid and exchange of acid, and consequently the pickling results obtained are not uniform; if the pickling operation is sustained for a period of time long enough to enable access of acid ibetween the adjacent surfaces, other portions of the coil will be overpickled.

Apparatus for pickling have been proposed, e.g. pickling tippers, which subject the material in the bath to up-down and to-fro movement, respectively. Thereby the relative motion between the charge to be pickled and the acid is enhanced and the pickling period shortened, differences in the results of pickling arising from the close proximity of individual windings are, however, not avoided.

Another known method for pickling coils and bundles consists in that the individual windings of a coil or the individual rods of a rod bundle are set in natural vibration by resonance and are thus caused to vehemently move in the pickling bath. In order to effect resonance with different ring diameters or with different dimensions of the material to be pickled, different frequencies must be employed, or else an entire frequency range must be run through, possibly more than once, so that the different elements of the material to be pickled are consecutively set vibrating. Furthermore, vibration nodes always form in those areas of the coil which contact with the support, wherefore less pickled spots are always found therein. Other portions, which move vehemently during resonance, show intensified pickling effects. Hence, follows that the overall pickling results vary over the cross section of the coil.

The present invention has as its object to avoid these disadvantages and difficulties and consists in that during the period of operation the vibration frequency is kept beyond the natural frequencies inherent in the vibratile parts, i.e. the individual windings of the coils, and that the vibration amplitude, in correspondence with the frequency, is so selected that the fall acceleration of the material to be pickled is exceeded and consequently to enable a short-time take-off of the material from the 3,592,690 Patented July 13, 1971 supporting device. During pickling a constant frequency, preferably below 16 Hz., is employed. The supporting device may be suspended on soft springs or rubber elastic elements and fixedly connected to vibrators, particularly unbalance motors. The supporting surface of the supporting device which the coil engages is preferably designed to have fiat flutes.

The method of the invention has the advantage that the contact and support areas of the individual coil windings move asunder, whenever for a short period of time a coil takes off from the supporting device, whereby fresh acid or the respective other liquid used is sucked in between those areas. Moreover, the areas of contact of the individual coil windings vary with every vibration. In this manner the method of the invention enables uniform pickling results over the entire surface of the coil and considerably shortens the pickling period.

During pickling one single frequency is employed for the vibrators which frequency must be selected so as to safeguard that neither the coil windings nor parts of the pickling device or the environments thereof are in resonance. In principle, any frequency may be chosen which meets the basic requirements that the energy of vibration is large enough to enable take-off of the supporting device from the coils. The maintenance of a frequency below 16 Hz. safeguards smooth operation of the apparatus. Suspension of the supporting devices on resilient springs or rubber elastic elements, the supporting device being directly connected to the vibrators, has the advantage that the transmission of uncontrollable forces to the supporting device or to the basement is avoided. Since during the vibration the material to be pickled takes off shortly from the support, the supporting device should be kept in horizontal direction, in order to avoid egression of the material to be pickled. If the supporting surface for the coils is flatly fluted this tendency toward egression is reduced, as even in slanting position of the supporting device the material to be pickled is retained on the ridges.

In order that the invention may be more fully understood an embodiment thereof will now be described by way of example with reference to the accompanying drawing.

A rail-supported transport vehicle 1 carries a hoist having two free rope ends, with a double-block arrangement on either side. One rope of each pair runs over the pulley 2 and holds the supporting device 5 in the position desired. The supporting device 5 is designed as a hanger with pickling hook 6 and suspended on soft draw springs 3. On both sides of the supporting device vibration-inducing unbalance motors 4 are arranged. The dot-and-dash lines indicate the coil 7 hanging on the pickling hook. The supporting surface of the hook 6 is flatly fluted, i.e. designed to have flat tops and clales as indicated by numeral 8, the forward end of the hook 6 is provided with a step-like elevation 9 preventing the coil 7 from sliding off or egress ing during pickling.

What I claim is:

1. In a method for pickling elongated stock wound to coils which are suspended on a supporting device to be immersed into a pickling bath, comprising subjecting said coils to vibration by vibrators acting on said supporting device, the improvement comprising the employment during operation of a vibration frequency which lies beyond the spectrum of natural frequencies of vibration inherent in the windings of said coils, and the employment of a vibration amplitude selected in dependence on said vibration frequency so as to be large enough to exceed fall acceleration of said coils and to consequently enable a a short-time take-off of said coils from said supporting device.

2. The method set forth in claim 1, wherein during MORRIS O. WO-LK, Primary Examiner pickling a constant frequency below 16 Hz. is employed. W F FINNEY Assistant Examiner References Cited cl- UNITED STATES PATENTS 5 134 2, 3, 14, 157, 164 1,738,412 12/1929 Williams 13414X 3,449,163 6/1969 Mobius et a1. 1343X 

